Tag Archives: Minamijima

Hirasea katoi Habe

Kato’s Hirasea Snail (Hirasea katoi)

Kato’s Hirasea Snail was described in 1973 based on only two specimens that were collected from dune deposits of probable Pleistocene age on the island of Minamijima in the Ogasawara archipealgo, Japan.

The shells reached sizes of 0,3 cm in height, they were very flat, opercular in shape with an extremely depressed spire and a sharply marginated periphery. [1]

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The species probably disappeared sometimes at the end of the Pleistocene or the beginning of the Holocene.

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References:

[1] Tadashige Habe: Fossil land snails from Minami-jima, Bonin Islands. Science Reports of the Tohoku University, Special Volume 6 (Hatai Memorial Volume): pages 51-53. 1973

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edited: 27.02.2024

Boninena hataii Habe

Hatai’s Boninea Snail (Boninena hataii)

Hatai’s Boninea Snail was described in 1973 on the basis of (sub)fossil shells that were recovered from deposits on the island of Minaijima in the Ogasawara archipelago, Japan.

The shells reach heights of about 1.3 cm; they are light brown, fusiform in shape with a highly conical spire of seven whorls and differ from those of their living relatives by being solid with a conical elevated spire and a large blunt apex. [1]

The species very likely disappeared before any humans set foot on the island caused by naturally occurring climatic changes.

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References:

[1] Tadashige Habe: Fossil land snails from Minami-jima, Bonin Islands. Science Reports of the Tohoku University, Special Volume 6 (Hatai Memorial Volume): 51-53. 1973

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edited: 27.02.2024

Hirasea minamijimana Habe

Minamijima Hirasea Snail (Hirasea minamijimana) 

The Minamijima Hirasea Snail was described in 1973 based on five specimens that were collected from probable Pleistocene deposits on the island of Minamijima, Ogasawara Islands, Japan. 

The shells reached sizes of about 0,56 to 0,64 cm in height; they were ashy white and their surface was ribbed by distantly placed rough growth lines. [1]

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I do not know for sure when this species actually disappeared, but I assume it to be a Pleistocene/Holocene border extinction.

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References:

[1] Tadashige Habe: Fossil land snails from Minami-jima, Bonin Islands. Science Reports of the Tohoku University, Special Volume 6 (Hatai Memorial Volume): 51-53. 1973

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edited: 11.05.2019

Mandarina luhuana ssp. minamijimana Chiba

Minamijima Mandarina Snail (Mandarina luhuana ssp. minamijimana)

The Minamijima Mandarina Snail was described in 2007, it is known exclusively from Holocene deposits on the island of Minamijima, Ogasawara Islands, Japan; it was originally thought to be identical with Mandarina luhuana (Sowerby) and was named as Mandarina luhuana f. A Chiba. 

The shells reach sizes of about 2.2 cm in height and up to 4.2 cm in diameter; they differ from those of the nominate race in having a higher spire, a smaller number of whorls, a relative narrower umbilicus and a thinner shell, the shells are furthermore darker in color. [1]

“Many fossil specimens of this species are found in the sand dune.” [1] (see also photo below)

The species likely disappeared at the Pleistocene/Holocene border due to natural climate changes.

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Photo: しんかわな – 投稿者が撮影
https://creativecommons.org/licenses/by/3.0/

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References:

[1] Tadashige Habe: Fossil land snails from Minami-jima, Bonin Islands. Science Reports of the Tohoku University, Special Volume 6 (Hatai Memorial Volume): 51-53. 1973
[2] Satoshi Chiba: Taxonomic revision of the fossil land snail species of the genus Mandarina in the Ogasawara Islands. Paleontological Research 11(4): 317-329. 2007

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edited: 27.02.2024

Mandarina titan Chiba

Giant Mandarina Snail (Mandarina titan)  

This species was described in 1989 based on fossil and subfossil material that had been collected from the fissure deposits of Minamijima Island, Ogasawara Islands, Japan. [1]

The Giant Mandarina Snail was indeed a giant, its shells reached sizes of up to nearly 7 to 8 cm in diameter, making it the largest land snail species of the Ogasawara Islands and also of Japan. [2]

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The species first appeared about 13000 BCE and finally disappeares from the deposits at around 8000 BCE in the early Holocene, it disappeared due to natural environmental changes. [1] 

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References:  

[1] Satoshi Chiba: Taxonomy and morphologic diversity of Mandarina (Pulmonata) in the Bonin Islands. Transactions and Proceedings – Palaeontological Society of Japan 155: 218-251. 1989
[2] Satoshi Chiba: Taxonomic revision of the fossil land snail species of the genus Mandarina in the Ogasawara Islands. Paleontological Research 11(4): 317-329. 2007

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edited: 19.04.2019